In USB (Universal-Serial Bus) or IEEE 1394 Bus, every device will be given one and only serial number or ID. Generally speaking, the processes for generating serial number at present can be divided into two kinds. Wherein one kind of the processes for generating serial number is to use a fixed serial number on devices of the same kind. Although this process is simple and convenient, the devices of the same kind cannot be connected to one and the same USB or IEEE 1394 Bus and be used normally.
The other commonly known process for generating serial number is to store the serial number of devices in ROM, EPROM, EEPROM or flash memory, in order to make the serial number one and only. However, this process will cause the increase of the cost for programming the serial number and the increase of the expenses for memory circuit components in the process of manufacturing the devices. Apart from this, it is necessary to have control to prevent the serial number from repetition in the process of manufacturing, and in order to have the function of control, a related control circuit must be provided accordingly.
In such a situation, the present invention provides a process for generating serial number from random number. The process is suitable for being used on devices that use a serial number in a bus. This process first generates the serial number for use from random number based on a seed number, it then checks whether the serial number for use is repeated in the bus. If the generated serial number for use repeats the serial number corresponding to any other devices of the same kind in the bus, a new serial number for use is generated.
Among these numbers, the seed number can be any of the serial number corresponding to any of the devices of the same kind in the bus. The serial number for use is obtained from the combination in a random way of the serial numbers corresponding to these devices of the same kind.
Apart from this, when the device is a scanner, the seed number can be obtained by the variability of the increase of the tube's brightness after the device is started, the brightness of the reflected light of the correcting board, the random noise of the Charge Couple Device (CCD), or the distance between the edge of the correcting board and the home position, or by other ways. If the serial number for use includes several digits, any one of the digits can be generated from the seed number obtained by any one of the ways for obtaining seed numbers.
To sum up, the present invention is to generate a needed serial number for use from random number. In most devices nowadays, a Central Processing Unit (CPU) is installed, therefor it will not be a problem to generate a random number. The invention can save time and the expense of related components, and can at the same time avoid the interference of the same serial numbers; thereby devices of the same kind can be installed on the same bus.
In order to make the above description and other objects, characteristics, and advantages of the invention clearer and easier to understand, A detailed description will be provided with preferred embodiments and with reference to the accompanying drawings as follows: